Hand prosthesis

1. A hand prosthesis comprising:

a hand chassis;

a thumb chassis mounted on the hand chassis for rotation of the thumb chassis in relation to the hand chassis about an axis extending generally along the length of the thumb chassis;

a thumb chassis motor disposed on the hand chassis, the thumb chassis motor being operable to drive a worm;

a worm gear wheel disposed on the thumb chassis, the worm being in engagement with the worm gear wheel such that, upon operation of the thumb chassis motor, the thumb chassis rotates in relation to the hand chassis; and

a thumb assembly,

wherein the thumb assembly attaches to the thumb chassis, the thumb assembly having a thumb motor positioned within the thumb assembly such that the thumb assembly moves at an angle to the hand chassis independently of the movement of the thumb chassis.

2. A hand prosthesis according to claim 1 , in which the worm gear wheel is disposed towards a proximal end of the thumb chassis.

3. A hand prosthesis according to claim 1 , in which the thumb chassis motor is operable to rotate about a first axis and the worm is operable to rotate about a second axis, the first and second axes being spaced apart from each other.

4. A hand prosthesis according to claim 3 , in which the first and second axes extend in substantially a same direction.

5. A hand prosthesis according to claim 1 , in which the hand prosthesis further comprises a coupling arrangement between the thumb chassis motor and the worm, the coupling arrangement being configured such that an axis of rotation of the worm differs from an axis of rotation of the thumb chassis motor.

6. A hand prosthesis according to claim 5 , in which the coupling arrangement comprises a gear arrangement configured to reduce a speed of rotation.

7. A hand prosthesis according to claim 5 , in which the hand prosthesis further comprises a plurality of gear arrangements, with a first gear arrangement forming part of the coupling arrangement and a second gear arrangement mechanically coupling the coupling arrangement to the worm.

8. A hand prosthesis according to claim 7 , in which the second gear arrangement is a planetary gear arrangement.

9. A hand prosthesis according to claim 1 , in which the thumb chassis is mechanically coupled to the hand chassis at a plurality of spaced apart locations.

10. A hand prosthesis according to claim 1 , in which the hand chassis comprises a platform extending in a plane generally orthogonal of a plane in which finger members of the hand prosthesis lie when the finger members are fully extended.

11. A hand prosthesis according to claim 10 , in which the hand chassis further comprises a palmar chassis extending in a plane generally orthogonal to the plane of the platform, the palmar chassis being configured for mounting of at least one digit member thereon.

12. A hand prosthesis according to claim 1 , in which the hand chassis comprises a bearing that is operative to provide for rotation of the thumb chassis in relation to the hand chassis.

13. A hand prosthesis according to claim 1 , in which the thumb assembly comprises at least two articulated portions, with a pair of articulated portions being movable in relation to each other about a joint.

14. A hand prosthesis according to claim 1 , in which the hand prosthesis further comprises at least one finger member attached to the hand chassis, with the finger member being configured for powered movement of articulated portions of the finger member.

15. A hand prosthesis according to claim 1 , in which the thumb chassis is rotatable about an axis extending away from a proximal end of the hand prosthesis.

16. A hand prosthesis according to claim 1 , in which the thumb chassis is rotatable about an axis substantially parallel to a plane defined by a palm of the hand prosthesis.

17. A hand prosthesis according to claim 1 , in which the hand prosthesis further comprises a position determining apparatus that is operative to determine a position of the thumb chassis.

18. A hand prosthesis according to claim 17 , in which the position determining apparatus comprises at least one position determining sensor that is operative to provide an electrical signal corresponding to a position of the thumb chassis.

19. A hand prosthesis according to claim 17 , in which the position determining apparatus comprises a plurality of switches, with each switch being operative when the thumb chassis is at a different position.

20. A hand prosthesis according to claim 17 , in which the position determining apparatus comprises a rotary position sensor.